Why do we need an in order, high power dissipation, low int performance chip in our computers? Cell isn't a general purpose chip, it's strongest area is number crunching, where new GPUs, Fermi and Cypress, are orders of magnitude faster.
In 2006-2007 it could have worked as an physics add on card, nowadays it wouldn't work.
And to the ones saying Sony should use with android in net tops, it dissipates ~20x the amount of power of a dual core atom, the batteries would last less than an hour, and you would have a hell to dissipate.